Comparison of classical fenton and fenton-like using µ-ZVI processes for the degradation of cresol in the wastewater

Abstract

The aim of this study was to investigate the applicability of a Fenton-like process using micron size zero valent iron (µ-ZVI) catalyst for the degradation of cresol in the wastewater, and the comparison of the degradation and the detoxification of cresol through this method and the classical Fenton process. The experiments were conducted in a batch reactor to examine the effects of pH, ZVI concentration, hydrogen peroxide concentration and temperature on the degradation of a wastewater containing 18.5 mM tricresol. The optimal reacting conditions were found to be pH = 2, [ZVI] = 5.35 g/L, [H2O2] = 472 mM and temperature = 30°C. The optimum conditions of the Fenton-like process were affected by corrosion phenomena and were different from the classical Fenton process. The evolutions of pH, cresol concentration, products concentration, dissolved iron concentration and chemical oxygen demand (COD) removal at the optimum conditions during the process were determined. At t = 120 min the efficiency of the degradation reaction reached at the maximum level (87.7%). The degradation efficiency obtained by the Fenton-like process is significantly higher in comparison with that achieved by the classical Fenton process (81.6%) at its optimum conditions. 85.8% of ZVI was recoverable by filtration after each experiment. The reusability of the recovered catalysts was also determined in 10 repetitive cycles (average degradation efficiency = 87.46%). Finally, bioassay tests for initial and treated wastewaters were conducted to evaluate their phytotoxicity on Lepidium sativum L. The phytotoxicity results were found to be in good accordance with the COD removals.